Search

The Biomedical Imaging and Therapy facility of the Canadian Light Source comprises two beamlines, which together cover a wide X-ray energy range from 13 keV up to 140 keV. The beamlines were designed with a focus on synchrotron applications in preclinical imaging and veterinary science as well as microbeam radiation therapy. While these remain a major part of the activities of both beamlines, a number of recent upgrades have enhanced the versatility and performance of the beamlines, particularly for high-resolution microtomography experiments. As a result, the user community has been quickly expanding to include researchers in advanced materials, batteries, fuel cells, agriculture, and environmental studies. This article summarizes the beam properties, describes the endstations together with the detector pool, and presents several application cases of the various X-ray imaging techniques available to users., (open access.)

The activity of basic multicellular units (BMU) in cortical bone is classically described as a sequential order of events- resorption, reversal and formation. This simplified portrayal of the remodeling process is pervasive despite the reported variability in remodeling space morphology. These variations may reflect meaningful nuances in BMU activity but methods to quantify 3D remodeling space morphology within the context of the cellular activity are currently lacking. This study developed new techniques to define zones of BMU activity based on the 3D morphology of remodeling spaces in rabbit cortical bone and integrated morphological data with the BMU longitudinal erosion rate (LER) to elucidate the spatial-temporal coordination of BMUs and estimate mineral apposition rate (MAR). The tibiae of New Zealand white rabbits (n = 5) were imaged in vivo using synchrotron radiation and two weeks later ex vivo with desktop microCT. The in vivo and ex vivo datasets were co-registered, and 27 remodeling spaces were identified at both timepoints. A radial profile representing the 3D morphology was the platform for partitioning the remodeling spaces into resorption, reversal and formation zones. Manual, automated and semi-automated partitioning approaches were compared, and the zone-segmentations were used to calculate the length, change in radius and slope of each zone. The manual approach most accurately defined the zones of idealized remodeling spaces with known dimensions (relative error = 0.9-9.2 %) while the semi-automated method reliably defined the zones in rabbit remodeling spaces (ICC = 0.85-1.00). Combining LER and the manually derived zone dimensions indicated that a BMU passes through a cross-section in approximately 18.8 days with resorption, reversal and formation taking 4.1, 2.2, and 12.5 days, respectively. MAR estimated by the 3D analysis was not significantly different than that determined with classic histomorphometry (p = 0.48). These techniques have the potential to assess dynamic parameters of bone resorption and formation, eliminate the need for fluorochrome labeling and provide a more comprehensive perspective of the remodeling process., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: David ML Cooper reports financial support was provided by Natural Sciences and Engineering Research Council of Canada., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Basic Multicellular Units (BMUs) conduct bone remodeling, a critical process of tissue turnover which, if imbalanced, can lead to disease, including osteoporosis. Parathyroid hormone (PTH 1-34; Teriparatide) is an osteoanabolic treatment for osteoporosis; however, it elevates the rate of intra-cortical remodeling (activation frequency) leading, at least transiently, to increased porosity. The purpose of this study was to test the hypothesis that PTH not only increases the rate at which cortical BMUs are initiated but also increases their progression (Longitudinal Erosion Rate; LER). Two groups (n = 7 each) of six-month old female New Zealand white rabbits were both administered 30 μg/kg of PTH once daily for a period of two weeks to induce remodeling. Their distal right tibiae were then imaged in vivo by in-line phase contrast micro-CT at the Canadian Light Source synchrotron. Over the following two weeks the first group (PTH) received continued daily PTH while the second withdrawal group (PTHW) was administrated 0.9 % saline. At four weeks all animals were euthanized, their distal tibiae were imaged by conventional micro-CT ex vivo and histomorphometry was performed. Matching micro-CT datasets (in vivo and ex vivo) were co-registered in 3D and LER was measured from 612 BMUs. Counter to our hypothesis, mean LER was lower (p < 0.001) in the PTH group (30.19 ± 3.01 μm/day) versus the PTHW group (37.20 ± 2.77 μm/day). Despite the difference in LER, osteonal mineral apposition rate (On.MAR) did not differ between groups indicating the anabolic effect of PTH was sustained after withdrawal. The slowing of BMU progression by PTH warrants further investigation; slowed resorption combined with elevated bone formation rate, may play an important role in how PTH enhances coupling between resorption and formation within the BMU. Finally, the prolonged anabolic response following withdrawal may have utility in terms of optimizing clinical dosing regimens., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Accurate evaluation of morphological changes in articular cartilage are necessary for early detection of osteoarthritis (OA). 3T magnetic resonance imaging (MRI) has highly sensitive contrast resolution and is widely used clinically to detect OA. However, synchrotron radiation phase-contrast imaging computed tomography (SR-PCI) can also provide contrast to tissue interfaces that do not have sufficient absorption differences, with the added benefit of very high spatial resolution. Here, MRI was compared with SR-PCI for quantitative evaluation of human articular cartilage. Medial tibial condyles were harvested from non-OA donors and from OA patients receiving knee replacement surgery. Both imaging methods revealed that average cartilage thickness and cartilage volume were significantly reduced in the OA group, compared to the non-OA group. When comparing modalities, the superior resolution of SR-PCI enabled more precise mapping of the cartilage surface relative to MRI. As a result, MRI showed significantly higher average cartilage thickness and cartilage volume, compared to SR-PCI. These data highlight the potential for high-resolution imaging of articular cartilage using SR-PCI as a solution for early OA diagnosis. Recognizing current limitations of using a synchrotron for clinical imaging, we discuss its nascent utility for preclinical models, particularly longitudinal studies of live animal models of OA., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Bairagi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objectives: In modern bone biology, the term "remodeling" generally refers to internal bone turnover that creates secondary osteons. However, it is also widely used by skeletal biologists, including biological anthropologists as a catch-all term to refer to different skeletal changes. In this review, we investigated how "remodeling" is used across topics on skeletal biology in biological anthropology to demonstrate potential problems with such pervasive use of a generalized term., Methods: Using PubMed and Google Scholar, we selected and reviewed 205 articles that use the term remodeling to describe skeletal processes and have anthropological implications. Nine edited volumes were also reviewed as examples of collaborative work by different experts to demonstrate the diverse and extensive use of the term remodeling., Results: Four general meanings of bone "remodeling" were identified, namely, internal turnover, functional adaptation, fracture repair, and growth remodeling. Additionally, remodeling is also used to refer to a broad array of pathological skeletal changes., Discussion: Although we initially identified four general meanings of bone remodeling, they are not mutually exclusive and often occur in combination. The term "remodeling" has become an extensively used catch-all term to refer to different processes and outcomes of skeletal changes, which inevitably lead to misunderstanding and a loss of information. Such ambiguity and confusion are potentially problematic as the field of biological anthropology becomes increasingly multidisciplinary. Therefore, we advocate for precise, context-specific definitions and explanations of bone remodeling as it continues to be used across disciplines within and beyond biological anthropology., (© 2023 Wiley Periodicals LLC.)

Background: Bone tissue engineering, based on three-dimensional (3D) printing technology, has emerged as a promising approach to treat bone defects using scaffolds. The objective of this study was to investigate the influence of porosity and internal structure on the mechanical properties of scaffolds., Methods: We fabricated composite scaffolds (which aimed to replicate trabecular bone) from polycaprolactone (PCL) reinforced with 30% (wt.) nano-hydroxyapatite (nHAp) by extrusion printing. Scaffolds with various porosities were designed and fabricated with and without an interlayer offset, termed as staggered and lattice structure, respectively. Mechanical compressive testing was performed to determine scaffold elastic modulus and yield strength. Linear regression was used to evaluate mechanical properties as a function of scaffold porosity., Results: Different relationships between mechanical properties and porosities were noted for the staggered and lattice structures. For elastic moduli, the two relationships intersected (porosity = 55%) such that the lattice structure exhibited higher moduli with porosity values greater than the intersection point; vice versa for the staggered structure. The lattice structure exhibited higher yield strength at all porosities. Mechanical testing results also indicated elastic moduli and yield strength properties comparable to trabecular bone (elastic moduli: 14-165 MPa; yield strength: 0.9-10 MPa)., Conclusions: Taken together, this study demonstrates that scaffolds printed from PCL/30% (wt.) nHAp with lattice and staggered structure offer promise for treating trabecular bone defects. This study identified the effect of porosity and internal structure on scaffold mechanical properties and provided suggestions for developing scaffolds with mechanical properties for substituting trabecular bone., (© 2023. The Author(s).)

Background: Scaffolds are of great importance in tissue engineering applications as they provide a mechanically supportive environment for cellular activity, which is particularly necessary for hard tissues such as bone. Notably, the mechanical properties of a scaffold vary with differing design parameters such as those related to scaffold height and internal structure. Thus, the present study aimed to explore the relationship between design parameters and mechanical properties of composite polycaprolactone (PCL) and nano-hydroxyapatite (nHAp) scaffolds fabricated by three-dimensional (3D) printing., Methods: We designed and printed scaffolds with different internal structures (lattice and staggered) and varying heights (4, 6, 8 and 10 layers), and consistent porosity (50%) for the purpose of comparison. Then, we examined the scaffold microstructure (pore size and penetration between layers) using scanning electron microscopy (SEM) and mechanical properties (elastic modulus and yield strength) using compressive testing., Results: Our results illustrated that the microstructural parameters were related to scaffold design. At higher heights, pore size increased while penetration between layers decreased; thus, mechanical properties were affected. Results of mechanical testing demonstrated that for lattice scaffolds, elastic modulus was similar for 6 vs 4, and 8 vs 4 layers but ~33% lower for 10 layers vs 4 layers. Similarly, yield strength was comparable for 6 vs 4, and 8 vs 4 layers but ~27% lower for 10 layers vs 4 layers. With staggered scaffolds, when compared to 4-layer results, elastic modulus was similar for 6 layers but was ~43% lower for 8 layers and ~38% lower for 10 layers. Staggered scaffolds had ~38%, ~51%, and ~76% lower yield strength when the number of layers were increased from 4 to 6, 8, and 10 layers, respectively. When comparing lattice and staggered scaffolds with the same layer number, elastic modulus was similar, apart from 8-layer scaffolds where the staggered design was ~42% lower than lattice. Yield strength was similar between 4-layer staggered and lattice scaffolds, while staggered scaffolds with 6, 8, and 10 number of layers showed ~43%, ~45%, ~68% lower strength, respectively, than those found in lattice scaffolds with the same layer numbers., Conclusions: Mechanical properties of 3D printed scaffolds depended on scaffold height for both lattice and staggered internal structures. Staggered scaffolds had lower mechanical properties than the lattice scaffolds with the same height and were more sensitive to the change in scaffold height. Taken together, lattice scaffolds demonstrated the advantages of more stable mechanical properties over staggered scaffolds. Also, scaffolds with lower height were more promising in terms of mechanical properties compared to scaffolds with greater height., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Yazdanpanah et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Temporal aspects of ligand specificity have been shown to play a significant role in the case of pulsatile hormone secretion, as exemplified by parathyroid hormone (PTH) binding to its receptor (PTH1R), a G-protein-coupled receptor expressed on surfaces of osteoblasts and osteocytes. The latter binding reaction regulates intracellular signalling and subsequently modulates skeletal homeostasis via bone remodelling. PTH glandular secretion patterns dictate bone cellular activity. In healthy humans, 70% of PTH is secreted in a tonic fashion, whereas 30% is secreted in low-amplitude and high-frequency bursts occurring every 10-20 min, superimposed on the tonic secretion. Changes in the PTH secretion patterns have been associated with various bone diseases. In this paper, we analyse PTH glandular secretion patterns for healthy and pathological states and their link to bone cellular responsiveness (αR). We utilise a two-state receptor ligand binding model of PTH to PTH1R together with a cellular activity function which is able to distinguish various aspects of the stimulation signal including peak dose, time of ligand exposure, and exposure period. Formulating and solving several constrained optimisation problems, we investigate the potential of pharmacological manipulation of the diseased glandular secretion and via clinical approved external PTH injections to restore healthy bone cellular responsiveness. Based on the mean experimentally reported data, our simulation results indicate cellular responsiveness in healthy subjects is sensitive to the tonic baseline stimulus and it is 28% of the computed maximum responsiveness. Simulation results for pathological cases of glucocorticoid-induced osteoporosis, hyperparathyroidism, initial and steady state hypocalcemia clamp tests indicate αR values significantly larger than the healthy baseline (1.7, 2.2, 4.9 and 1.9-times, respectively). Manipulation of the pulsatile glandular secretion pattern, while keeping the mean PTH concentration constant, allowed restoration of healthy baseline values from these catabolic bone diseases. Conversely, PTH glandular diseases that led to maximum bone cellular responsiveness below the healthy baseline value can't be restored to baseline via glandular manipulation. However, external PTH injections allowed restoration of these latter cases., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Martonová et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Visualization of low-density tissue scaffolds made from hydrogels is important yet challenging in tissue engineering and regenerative medicine (TERM). For this, synchrotron radiation propagation-based imaging computed tomography (SR-PBI-CT) has great potential, but is limited due to the ring artifacts commonly observed in SR-PBI-CT images. To address this issue, this study focuses on the integration of SR-PBI-CT and helical acquisition mode (i.e. SR-PBI-HCT) to visualize hydrogel scaffolds. The influence of key imaging parameters on the image quality of hydrogel scaffolds was investigated, including the helical pitch (p), photon energy (E) and the number of acquisition projections per rotation/revolution (N p ), and, on this basis, those parameters were optimized to improve image quality and to reduce noise level and artifacts. The results illustrate that SR-PBI-HCT imaging shows impressive advantages in avoiding ring artifacts with p = 1.5, E = 30 keV and N p = 500 for the visualization of hydrogel scaffolds in vitro. Furthermore, the results also demonstrate that hydrogel scaffolds can be visualized using SR-PBI-HCT with good contrast while at a low radiation dose, i.e. 342 mGy (voxel size of 26 µm, suitable for in vivo imaging). This paper presents a systematic study on hydrogel scaffold imaging using SR-PBI-HCT and the results reveal that SR-PBI-HCT is a powerful tool for visualizing and characterizing low-density scaffolds with a high image quality in vitro. This work represents a significant advance toward the non-invasive in vivo visualization and characterization of hydrogel scaffolds at a suitable radiation dose., (open access.)

Cellular communication in the mechanosensory osteocyte Lacuno-Canalicular Network (LCN) regulates bone tissue remodeling throughout life. Age-associated declines in LCN size and connectivity dysregulate mechanosensitivity to localized remodeling needs of aging or damaged tissue, compromising bone quality. Synchrotron radiation-based micro-Computed Tomography (SRμCT) and Confocal Laser Scanning Microscopy (CLSM) were employed to visualize LCN and vascular canal morphometry in an age series of the anterior femur (males n = 14, females n = 11, age range = 19-101, mean age = 55). Age-associated increases in vascular porosity were driven by pore coalescence, including a significant expansion in pore diameter and a significant decline in pore density. In contrast, the LCN showed significant age-associated reductions in lacunar volume fraction, mean diameter, and density, and in canalicular volume fraction and connectivity density. Lacunar density was significantly lower in females across the lifespan, exacerbating their age-associated decline. Canalicular connectivity density was also significantly lower in females but approached comparable declining male values in older age. Our data illuminate the trajectory and potential morphometric sources of age-associated bone loss. Increased vascular porosity contributes to bone fragility with aging, while an increasingly reduced and disconnected LCN undermines the mechanosensitivity required to repair and reinforce bone. Understanding why and how this degradation occurs is essential for improving the diagnosis and treatment of age-related changes in bone quality and fragility., (© 2022 American Association for Anatomy.)

The food industry has long been searching for an efficient replacement for saturated-fatty-acid-rich fats for baking applications. Although oleogels have been considered a potential alternative for saturated and trans fats, their success in food application has been poor. The present study explored the use of oleofoams obtained by whipping the pulse protein foam-templated oleogels for cake baking. Oleogels were prepared at room temperature by adding canola oil containing high-melting monoglyceride (MAG) or candelilla wax (CW) to the freeze-dried pea or faba bean protein-stabilized foams. Oleogels were then whipped to create the oleofoams; however, only the oleogels containing MAG could form oleofoams. CW-oleogel could not form any oleofoam. The most stable oleofoams with the highest overrun, stability, and storage modulus were obtained from 3% MAG+pulse protein foam-templated oleogels. The MAG plus protein foam-templated oleogels showed smaller and more packed air bubbles than MAG-only oleofoam, which was ascribed to the protein's ability to stabilize air bubbles and provide a network in the continuous oil phase to restrict air bubble movement. A novel batter preparation method for oleofoam was developed to increase air bubble incorporation. The X-ray microtomography images of the cakes showed a non-homogeneous distribution of larger air bubbles in the oleofoam cake compared to the shortening cake although their total porosity was not much different. The oleofoam cakes made with the new method yielded similar hardness and chewiness compared to the shortening cakes. By improving rheology and increasing air incorporation in the batter, high-quality cakes can be obtained with MAG-containing oleofoams made from pulse protein foam-templated oleogels.

Simulated microgravity (SMG) inhibits osteoblast differentiation (OBD) and induces bone loss via the inhibition of the Wnt/β-catenin pathway. However, the mechanism by which SMG alters the Wnt/β-catenin pathway is unknown. We previously demonstrated that SMG altered the focal adhesion kinase (FAK)-regulated mTORC1, AMPK and ERK1/2 pathways, leading to the inhibition of tumor cell proliferation/metastasis and promoting cell apoptosis. To examine whether FAK similarly mediates SMG-dependent changes to Wnt/β-catenin in osteoblasts, we characterized mouse MC3T3-E1 cells cultured under clinostat-modeled SMG (µg) conditions. Compared to cells cultured under ground (1 g) conditions, SMG reduces focal adhesions, alters cytoskeleton structures, and down-regulates FAK, Wnt/β-catenin and Wnt/β-catenin-regulated molecules. Consequently, protein-2 (BMP2), type-1 collagen (COL1), alkaline-phosphatase activity and matrix mineralization are all inhibited. In the mouse hindlimb unloading (HU) model, SMG-affected tibial trabecular bone loss is significantly reduced, according to histological and micro-computed tomography analyses. Interestingly, the FAK activator, cytotoxic necrotizing factor-1 (CNF1), significantly suppresses all of the SMG-induced alterations in MC3T3-E1 cells and the HU model. Therefore, our data demonstrate the critical role of FAK in the SMG-induced inhibition of OBD and bone loss via the Wnt/β-catenin pathway, offering FAK signaling as a new therapeutic target not only for astronauts at risk of OBD inhibition and bone loss, but also osteoporotic patients.

Treating large bone defects, known as critical-sized defects (CSDs), is challenging because they are not spontaneously healed by the patient's body. Due to the limitations associated with conventional bone grafts, bone tissue engineering (BTE), based on three-dimensional (3D) bioprinted scaffolds, has emerged as a promising approach for bone reconstitution and treatment. Bioprinting technology allows for incorporation of living cells and/or growth factors into scaffolds aiming to mimic the structure and properties of the native bone. To date, a wide range of biomaterials (either natural or synthetic polymers), as well as various cells and growth factors, have been explored for use in scaffold bioprinting. However, a key challenge that remains is the fabrication of scaffolds that meet structure, mechanical, and osteoconductive requirements of native bone and support vascularization. In this review, we briefly present the latest developments and discoveries of CSD treatment by means of bioprinted scaffolds, with a focus on the biomaterials, cells, and growth factors for formulating bioinks and their bioprinting techniques. Promising state-of-the-art pathways or strategies recently developed for bioprinting bone scaffolds are highlighted, including the incorporation of bioactive ceramics to create composite scaffolds, the use of advanced bioprinting technologies ( e.g. , core/shell bioprinting) to form hybrid scaffolds or systems, as well as the rigorous design of scaffolds by taking into account of the influence of such parameters as scaffold pore geometry and porosity. We also review in-vitro assays and in-vivo models to track bone regeneration, followed by a discussion of current limitations associated with 3D bioprinting technologies for BTE. We conclude this review with emerging approaches in this field, including the development of gradient scaffolds, four-dimensional (4D) printing technology via smart materials, organoids, and cell aggregates/spheroids along with future avenues for related BTE., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Yazdanpanah, Johnston, Cooper and Chen.)

Ancestors of the Antarctic icefishes (family Channichthyidae) were benthic and had no swim bladder, making it energetically expensive to rise from the ocean floor. To exploit the water column, benthopelagic icefishes were hypothesized to have evolved a skeleton with "reduced bone," which gross anatomical data supported. Here, we tested the hypothesis that changes to icefish bones also occurred below the level of gross anatomy. Histology and micro-CT imaging of representative craniofacial bones (i.e., ceratohyal, frontal, dentary, and articular) of extant Antarctic fish species specifically evaluated two features that might cause the appearance of "reduced bone": bone microstructure (e.g., bone volume fraction and structure linear density) and bone mineral density (BMD, or mass of mineral per volume of bone). Measures of bone microstructure were not consistently different in bones from the icefishes Chaenocephalus aceratus and Champsocephalus gunnari, compared to the related benthic notothenioids Notothenia coriiceps and Gobionotothen gibberifrons. Some quantitative measures, such as bone volume fraction and structure linear density, were significantly increased in some icefish bones compared to homologous bones of non-icefish. However, such differences were rare, and no microstructural measures were consistently different in icefishes across all bones and species analyzed. Furthermore, BMD was similar among homologous bones of icefish and non-icefish Antarctic notothenioids. In summary, "reduced bone" in icefishes was not due to systemic changes in bone microstructure or BMD, raising the prospect that "reduced bone" in icefish occurs only at the gross anatomic level (i.e., smaller or fewer bones). Given that icefishes exhibit delayed skeletal development compared to non-icefish Antarctic fishes, combining these phenotypic data with genomic data might clarify genetic changes driving skeletal heterochrony., (© 2021 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Bones represent a valuable biological archive of environmental lead (Pb) exposure for modern and archaeological populations. Synchrotron radiation X-ray fluorescence imaging (SR-XFI) generates maps of Pb in bone on a microstructural scale, potentially providing insights into an individual's history of Pb exposure and, in the context of archaeological bone, the biogenic or diagenetic nature of its uptake. The aims of this study were to (1) examine biogenic spatial patterns for Pb from bone samples of modern cadavers compared with patterns observed archaeologically, and (2) test the hypothesis that there are spatial differences in the distribution of Pb for diagenetic and biogenic modes of uptake in bone. To address these aims, this study used inductively coupled plasma-mass spectrometry (ICP-MS) and SR-XFI on unaltered and experimentally altered cadaveric bone samples (University of Saskatchewan, Saskatoon, SK) and archaeological bone samples from 18th to 19th century archaeological sites from Antigua and Lithuania. Bone concentrations of modern individuals are relatively low compared to those of archaeological individuals. SR-XFI results provide insights into modern Saskatchewan Pb exposure with some samples demonstrating a pattern of relatively low Pb exposure with higher levels of Pb exposure occurring in bone structures of a relatively older age that formed earlier in life, likely during the era of leaded gasoline (pre-1980s), and other samples demonstrating a pattern of fairly consistent, low-level exposure. Results support hypotheses for the spatial distribution of Pb corresponding to biogenic vs. diagenetic uptake. Diagenetic Pb is mainly confined to the periosteal surface of each sample with some enrichment of cracks and sub-periosteal canals. This may be useful in the future for differentiating diagenetic from biogenic Pb accumulation, analyzing environmental contamination, and informing sampling strategies in archaeological or fossil bone., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

For humans and other mammals to eat effectively, teeth must develop properly inside the jaw. Deciphering craniodental integration is central to explaining the timely formation of permanent molars, including third molars which are often impacted in humans, and to clarifying how teeth and jaws fit, function and evolve together. A factor long-posited to influence molar onset time is the jaw space available for each molar organ to form within. Here, we tested whether each successive molar initiates only after a minimum threshold of space is created via jaw growth. We used synchrotron-based micro-CT scanning to assess developing molars in situ within jaws of C57BL/6J mice aged E10 to P32, encompassing molar onset to emergence. We compared total jaw, retromolar and molar lengths, and molar onset times, between upper and lower jaws. Initiation time and developmental duration were comparable between molar upper and lower counterparts despite shorter, slower-growing retromolar space in the upper jaw, and despite size differences between upper and lower molars. Timing of molar formation appears unmoved by jaw length including space. Conditions within the dental lamina likely influence molar onset much more than surrounding jaw tissues. We theorize that molar initiation is contingent on sufficient surface area for the physical reorganization of dental epithelium and its invagination of underlying mesenchyme.

Objectives: This research focused on osteoarthritis (OA) lesions on modern patients to 1) identify consistently observed lesions not included within current paleopathological measures of OA, 2) assess the correspondence of bone and cartilage lesions with clinical OA diagnostic criteria, and 3) discuss the correspondence of bone lesions with sources of pain reported in clinical literature., Materials: Tibial plateaus from 62 patients undergoing total knee replacement surgery due to OA were examined., Methods: Plateaus were scored for several non-standard OA criteria, including non-articular and X-ray visible lesions and pre-maceration cartilage lesions, as well as articular surface criteria standard in paleopathology., Results: Proliferative bone in the intercondylar region was present in 95 % of specimens, while areas of dense trabecular bone and lytic defects, both on the inferior side of the plateaus, were present in 98 % and 83 %, respectively., Conclusions: The inferior lytic defects may be physical evidence of bone marrow lesions (BML), a clinical OA indicator visible via MRI. Previous research has linked BML to pain, inflammation, and ligament pathology. The latter conditions have also been associated with intercondylar enthesophytes and third intercondylar tubercle of Parsons (TITP), both of which were observed in the intercondylar regions., Significance: Several non-articular lesions not currently included in paleopathological measures of OA were consistently observed., Suggestions for Future Research: A similar analysis of a control sample of non-OA tibial plateaus would better contextualize these results., Limitations: The sample's high average age (65.8 years) and severe OA stage may hamper generalizability to archaeological collections., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to evaluate the efficacy and toxicity of a novel lanthanum compound, La(XT), in an ovariectomized (OVX) rat model of osteoporosis., Methods: Twenty-four ovariectomized female Sprague Dawley rats were divided into 3 groups receiving a research diet with/without treatment compounds (alendronate: 3 mg/kg; La(XT) 100 mg/kg) for three months. At the time of sacrifice, the kidney, liver, brain, lung and spleen were collected for histological examination. The trabecular bone structure of the tibiae was evaluated using micro-CT and a three-point metaphyseal mechanical test was used to evaluate bone failure load and stiffness., Results: No significant differences were noted in plasma levels of calcium, phosphorus, creatinine, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) between the La(XT) treatment compared to the non-treated OVX group. Alendronate-treated animals (positive control) showed higher BV/TV, Tb.N and lower Tb.Th and Tb.Sp when compared to the non-treated OVX group. Mechanical analysis indicated that stiffness was higher in the alendronate (32.88%, p = 0.04) when compared to the non-treated OVX group. Failure load did not differ among the groups., Conclusions: No kidney or liver toxicities of La(XT) treatments were found during the three-month study. The absence of liver and kidney toxicity with drug treatment for 3 months, as well as the increased trabecular bone stiffness are encouraging for the pursuit of further studies with La(XT) for a longer duration of time., Competing Interests: All authors listed in this paper declare no conflict of interest. Animal studies were approved by the University of Saskatchewan Animal Care Committee (Protocol #20150060), and performed in accordance with the guidelines outlined by the Canadian Council on Animal Care (CCAC). Funding for this study was provided by a 10.13039/501100000106Saskatchewan Health Research Foundation Establishment Grant (SHRF to K.M.W.). We acknowledge the Natural Sciences and Engineering Research Council (NSERC) of Canada for CGSM/CGSD fellowships (T.I.K.), the IsoSiM 10.13039/501100000038NSERC CREATE program at TRIUMF for their generous support (T.I.K.) and a Discovery Grant (C.O.)., (© 2021 The Author(s).)

Background: It is known that a number of parameters can influence the post-printing properties of bone tissue scaffolds. Previous research has primarily focused on the effect of parameters associated with scaffold design (e.g., scaffold porosity) and specific scaffold printing processes (e.g., printing pressure). To our knowledge, no studies have investigated variations in post-printing properties attributed to the techniques used to synthesize the materials for printing (e.g., melt-blending, powder blending, liquid solvent, and solid solvent)., Methods: Four material preparation techniques were investigated to determine their influence on scaffold properties. Polycaprolactone/nano-hydroxyapatite 30% (wt.) materials were synthesized through melt-blending, powder blending, liquid solvent, and solid solvent techniques. The material printability and the properties of printed scaffolds, in terms of swelling/degradation, mechanical strength, morphology, and thermal properties, were examined and compared to one another using Kruskal-Wallis nonparametric statistical analysis., Results: Material prepared through the liquid solvent technique was found to have limited printability, while melt-blended material demonstrated the highest degree of uniformity and lowest extent of swelling and degradation. Scaffolds prepared with powder-blended material demonstrated the highest Young's modulus, yield strength, and modulus of resilience; however, they also demonstrated the highest degree of variability. The higher degree of inhomogeneity in the material was further supported by thermal gravimetric analysis. While scaffolds printed from melt-blended, powder-blended, and solid solvent materials demonstrated a high degree of micro-porosity, the liquid solvent material preparation technique resulted in minimal micro-porosity., Conclusions: Study results indicate that specific techniques used to prepare materials influence the printing process and post-printing scaffold properties. Among the four techniques examined, melt-blended materials were found to be the most favorable, specifically when considering the combination of printability, consistent mechanical properties, and efficient preparation. Techniques determined to be favourable based on the properties investigated should undergo further studies related to biological properties and time-dependent properties beyond 21-days.

Given their strong affinity for the skeleton, trace elements are often stored in bones and teeth long term. Diet, geography, health, disease, social status, activity, and occupation are some factors which may cause differential exposure to, and uptake of, trace elements, theoretically introducing variability in their concentrations and/or ratios in the skeleton. Trace element analysis of bioarchaeological remains has the potential, therefore, to provide rich insights into past human lifeways. This review provides a historical overview of bioarchaeological trace element analysis and comments on the current state of the discipline by highlighting approaches with growing momentum. Popularity for the discipline surged following preliminary studies in the 1960s to 1970s that demonstrated the utility of strontium (Sr) as a dietary indicator. During the 1980s, Sr/Ca ratio and multi-element studies were commonplace in bioarchaeology, linking trace elements with dietary phenomena. Interest in using trace elements for bioarchaeological inferences waned following a period of critiques in the late 1980s to 1990s that argued the discipline failed to account for diagenesis, simplified complex element uptake and regulation processes, and used several unsuitable elements for palaeodietary reconstruction (e.g. those under homeostatic regulation, those without a strong affinity for the skeleton). In the twenty-first century, trace element analyses have been primarily restricted to Sr and lead (Pb) isotope analysis and the study of toxic trace elements, though small pockets of bioarchaeology have continued to analyse multiple elements. Techniques such as micro-sampling, element mapping, and non-traditional stable isotope analysis have provided novel insights which hold the promise of helping to overcome limitations faced by the discipline., Supplementary Information: The online version contains supplementary material available at 10.1007/s12520-020-01262-4., Competing Interests: Conflict of interestThe authors declare they have no conflicts of interest., (© The Author(s) 2021.)

One of only a few approved and available anabolic treatments for severe osteoporosis is daily injections of PTH (1-34). This drug has a specific dual action which can act either anabolically or catabolically depending on the type of administration, i.e. intermittent or continuous, respectively. In this paper, we present a mechanistic pharmacokinetic-pharmacodynamic model of the action of PTH in postmenopausal osteoporosis. This model accounts for anabolic and catabolic activities in bone remodelling under intermittent and continuous administration of PTH. The model predicts evolution of common bone biomarkers and bone volume fraction (BV/TV) over time. We compared the relative changes in BV/TV resulting from a daily injection of 20 [Formula: see text]g of PTH with experimental data from the literature. Simulation results indicate a site-specific bone gain of 8.66[Formula: see text] (9.4 ± 1.13[Formula: see text]) at the lumbar spine and 3.14[Formula: see text] (2.82 ± 0.72[Formula: see text]) at the femoral neck. Bone gain depends nonlinearly on the administered dose, being, respectively, 0.68[Formula: see text], 3.4[Formula: see text] and 6.16[Formula: see text] for a 10, 20 and 40 [Formula: see text]g PTH dose at the FN over 2 years. Simulations were performed also taking into account a bone mechanical disuse to reproduce elderly frail subjects. The results show that mechanical disuse ablates the effects of PTH and leads to a 1.08% reduction of bone gain at the FN over a 2-year treatment period for the 20 [Formula: see text]g of PTH. The developed model can simulate a range of pathological conditions and treatments in bones including different PTH doses, different mechanical loading environments and combinations. Consequently, the model can be used for testing and generating hypotheses related to synergistic action between PTH treatment and physical activity.

This paper introduces a theoretical framework for the study of the efficacy of romosozumab, a humanized monoclonal antibody targeting sclerostin for the treatment of osteoporosis. We developed a comprehensive mechanistic pharmacokinetic-pharmacodynamic (PK-PD) model of the effect of drug treatment on bone remodeling in postmenopausal osteoporosis (PMO). We utilized a one-compartment PK model to represent subcutaneous injections of romosozumab and subsequent absorption into serum. The PD model is based on a recently-developed bone cell population model describing the bone remodeling process at the tissue scale. The latter accounts for mechanical feedback by incorporating nitric oxide (NO) and sclerostin (Scl) as biochemical feedback molecules. Utilizing a competitive binding model, where Wnt and Scl compete for binding to LRP5/6, allows to regulate anabolic bone remodeling responses. Here, we extended this model with respect to romosozumab binding to sclerostin. For the currently approved monthly injections of 210 mg, the model predicted a 6.59%, 10.38% and 15.25% increase in BMD at the lumbar spine after 6, 12 and 24 months, respectively. These results are in good agreement with the data reported in the literature. Our model is also able to distinguish the bone-site specific drug effects. For instance, at the femoral neck, our model predicts a BMD increase of 3.85% after 12 months of 210 mg injections, which is consistent with literature observations. Finally, our simulations indicate rapid bone loss after treatment discontinuation, indicating that some additional interventions such as use of bisphosphonates are required to maintain bone mass., Competing Interests: Declaration of competing interest The authors do not have anything to disclose., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Many mechanical properties of cortical bone are largely governed by the underlying microarchitecture; however, the influence of microarchitecture on the fatigue life of bone is poorly understood. Furthermore, imaging-based studies investigating intracortical microarchitecture may expose bone samples to large doses of radiation that may compromise fatigue resistance. The purpose of this pilot study was to 1) investigate the relationship between intracortical microarchitecture and the fatigue life of human bone in compression and 2) examine the effects of synchrotron irradiation on fatigue life measurements. Cortical samples were prepared from the femoral and tibial shafts of three cadaveric donors. A subset of samples was imaged using synchrotron X-ray microCT to quantify microarchitecture, including porosity, canal diameter, lacunar density, lacunar volume, and lacunar orientation. A second group of control samples was not imaged and used only for mechanical testing. Fatigue life was quantified by cyclically loading both groups in zero-compression until failure. Increased porosity and larger canal diameter were both logarithmically related to a shorter fatigue life, whereas lacunar density demonstrated a positive linear relationship with fatigue life (r 2  = 45-73%, depending on measure). Irradiation from microCT scanning reduced fatigue life measurements by 91%, but relationships with microarchitecture measurements remained. Additional research is needed to support the findings of this pilot study and fully establish the relationship between intracortical microarchitecture and the compressive fatigue life of bone., (© 2020 The Authors.)

Uncontrolled diabetes is associated with increased risk of bony fractures. However, the mechanisms have yet to be understood. Using high-resolution synchrotron micro-CT, we calculated the changes in the microstructure of femoral cortices of streptozotocin-induced hyperglycemic (STZ) Wistar Albino rats and tested the mechanical properties of the mineralized matrix by nanoindentation. Total lacunar volume of femoral cortices increased in STZ group due to a 9% increase in lacunar density. However, total vascular canal volume decreased in STZ group due to a remarkable decrease in vascular canal diameter (7 ± 0.3 vs. 8.5 ± 0.4 µm). Osteocytic territorial matrix volume was less in the STZ group (14,908 ± 689 µm 3 ) compared with healthy controls (16,367 ± 391 µm 3 ). In conclusion, hyperglycemia increased cellularity and lacunar density, decreased osteocyte territorial matrix, and reduced vascular girth, in addition to decreasing matrix mechanical properties in the STZ group when compared with euglycemic controls.

Significant progress has been made to identify the cells and signaling molecules involved in the mechanobiological regulation of bone remodeling. It is now well accepted that osteocytes act as mechanosensory cells in bone expressing several signaling molecules such as nitric oxide (NO) and sclerostin (Scl) which are able to control bone remodeling responses. In this paper, we present a comprehensive multiscale computational model of bone remodeling which incorporates biochemical osteocyte feedback. The mechanostat theory is quantitatively incorporated into the model using mechanical feedback to control expression levels of NO and Scl. The catabolic signaling pathway RANK-RANKL-OPG is co-regulated via (continuous) PTH and NO, while the anabolic Wnt signaling pathway is described via competitive binding reactions between Wnt, Scl and the Wnt receptors LRP5/6. Using this novel model of bone remodeling, we investigate the effects of changes in the mechanical loading and hormonal environment on bone balance. Our numerical simulations show that we can calibrate the mechanostat anabolic and catabolic regulatory mechanisms so that they are mutually exclusive. This is consistent with previous models that use a Wolff-type law to regulate bone resorption and formation separately. Furthermore, mechanical feedback provides an effective mechanism to obtain physiological bone loss responses due to mechanical disuse and/or osteoporosis.

This paper presents a pharmacokinetic/pharmacodynamic (PK/PD) model of the action of PTH(1-34) on bone modelling and remodelling, developed for quantitatively investigating the dose- and administration pattern-dependency of the bone tissue response to this drug. Firstly, a PK model of PTH(1-34) was developed, accounting for administration via subcutaneous injections. Subsequently, the PK model was coupled to a (mechanistic) bone cell population model of bone modelling and remodelling, taking into account the effects of PTH(1-34) on the differentiation of lining cells into active osteoblasts, on the apoptosis of active osteoblasts, and on proliferation of osteoblast precursors, as well as on the key regulatory pathways of bone cell activities. Numerical simulations show that the coupled PK/PD model is able to distinguish between continuous and intermittent administration patterns of PTH(1-34), in terms of yielding both catabolic bone responses (if drug administration is carried out continuously) and anabolic bone responses (if drug administration is carried out intermittently). The model also features a non-linear relation between bone gain and drug dose (as known from experiments); doubling the dose from 80 μg/kg/day to 160 μg/kg/day induced a 1.3-fold increase of the bone volume-to-total volume ratio. Furthermore, the model presented in this paper confirmed that bone modelling represents an essential mechanism of the anabolic response of bone to PTH(1-34) administration in rat models, and that the large amount of bone formation observed in such models cannot be explained via remodelling alone., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Bone acts as a reservoir for many trace elements. Understanding the extent and pattern of elemental accumulation in the skeleton is important from diagnostic, therapeutic, and toxicological perspectives. Some elements are simply adsorbed to bone surfaces by electric force and are buried under bone mineral, while others can replace calcium atoms in the hydroxyapatite structure. In this article, we investigated the extent and pattern of skeletal uptake of barium and strontium in two different age groups, growing, and skeletally mature, in healthy rats. Animals were dosed orally for 4 weeks with either strontium chloride or barium chloride or combined. The distribution of trace elements was imaged in 3D using synchrotron K-edge subtraction micro-CT at 13.5 µm resolution and 2D electron probe microanalysis (EPMA). Bulk concentration of the elements in serum and bone (tibiae) was also measured by mass spectrometry to study the extent of uptake. Toxicological evaluation did not show any cardiotoxicity or nephrotoxicity. Both elements were primarily deposited in the areas of active bone turnover such as growth plates and trabecular bone. Barium and strontium concentration in the bones of juvenile rats was 2.3 times higher, while serum levels were 1.4 and 1.5 times lower than adults. In all treatment and age groups, strontium was preferred to barium even though equal molar concentrations were dosed. This study displayed spatial co-localization of barium and strontium in bone for the first time. Barium and strontium can be used as surrogates for calcium to study the pathological changes in animal models of bone disease and to study the effects of pharmaceutical compounds on bone micro-architecture and bone remodeling in high spatial sensitivity and precision.

Based on a well-preserved specimen from Eocene Baltic amber, the second fossil species belonging to the genus Pycnomerus Erichson (Coleoptera: Zopheridae: Zopherinae), P. agtsteinicus Bukejs, Alekseev McKellar sp. nov. is described and illustrated using synchrotron X-ray micro-CT observations. The new species adds to the sparse fossil record of Pycnomerus, which consists of the Baltic amber discoveries, and only four subfossil records in sediments that are less than one million years old. As part of this work, the new replacement name Pycnomerus lordi Bukejs, Alekseev McKellar nom. nov. is also established for the extant species Pycnomerus sulcicollis LeConte, 1863 [non Pycnomerus sulcicollis (Germar, 1824)].

Bone is a defining characteristic of the vertebrate skeleton, and while chondrichthyans (sharks, skates, and other cartilaginous fishes) are vertebrates, they are hypothesized to have lost the ability to make bone during their evolution. Multiple descriptions of a bone-like tissue in neural arches of vertebrae in various shark species (selachians), however, challenge this hypothesis. Here, we extend this argument by analyzing vertebrae of two members of the batoids (the little skate Leucoraja erinacea and Eaton's skate Bathyraja eatonii), the sister group to selachians within elasmobranchs. Micro-CT images showed a bone-like mineralization pattern in neural arches of each skate species, and histological analyses confirmed that this bone-like tissue surrounded a cartilage core, exactly as described in sharks. Another mineralization pattern identified in skate vertebrae was distinct from the polygonal tesseral and areolar patterns that classically are associated with the chondrichthyan endoskeleton. Many regions of the vertebrae, including the neural spine and transverse processes, showed this perichondral mineralization pattern, termed here trabecular tesseral. Other than the cartilage core of the neural arch, all mineralized tissues in skate vertebrae had flattened cells surrounded by matrix with bone-like histology. Analyses of quantitative microstructural parameters revealed that, compared to rat vertebrae, the bone-like mineralization pattern in the neural arches of skate vertebrae was more similar to compact bone than trabecular bone. In contrast, the thickness of the trabecular tesseral pattern was more similar to trabecular bone than compact bone of rat vertebrae. In conclusion, a bone-like tissue in neural arches of skate vertebrae appears to be a novel elasmobranch synapomorphy. We propose that the trabecular tesseral mineralization pattern in the skate might have deep homology to the mineralization pattern utilized in trabecular bone. STATEMENT OF SIGNIFICANCE: Mineralization patterns of skeletal tissues have not been investigated thoroughly in all vertebrate clades. Despite their designation as 'cartilaginous fish', chondrichthyans clearly evolved from ancestral vertebrates that made bone. The consensus that chondrichthyans lost the ability to make bone during their evolution, however, is challenged by reports of bone and bone-like tissues in the neural arches of vertebrae in extant sharks (selachians). Here, we provide evidence from micro-CT imaging and histological analyses to support our hypothesis that a bone-like tissue is present in the neural arches of batoids (the sister group to selachians within elasmobranchs). These results argue strongly that the neural arch bone-like tissue is a previously unknown synapomorphy of elasmobranchs. In addition to the bone-like mineralization pattern identified in the neural arches, micro-CT images also showed a novel mineralization pattern which we described as trabecular tesseral. Quantitative microstructural features shared between trabecular tesseral pattern and trabecular bone (from homologous rat vertebrae) suggest that both patterns might derive from an ancestral gene network driving trabecular mineralization (i.e., deep homology)., (Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Visualizing tooth organs from their earliest inception as they actually appear in three dimensions has, until recently, been difficult due to the technical obstacle of imaging these tiny, translucent, low-density embryonic craniodental tissues. Related to this obstacle, quantifying craniodental morphology has been confounded by the time consuming need to physically section and then digitally photograph and reconstruct these images of tissues into 3D volumes. Here we provide a simple solution in the form of an overnight silver albumin tissue stain for whole embryos. Because it is differentially absorbed by embryonic tissues, this stain generates the contrast needed to detect and visualize unmineralized dental tissues. Stained specimens can be scanned using either desktop or synchrotron micro-computed tomography systems, generating digital 3D datasets of whole embryos that can immediately be used to assess dental morphology and histology. Craniodental structures can then be measured with high precision and accuracy using 3D image analysis software.

High-resolution synchrotron computed tomography (CT) is very helpful in the diagnosis and monitor of chronic diseases including osteoporosis. Osteoporosis is characterized by low bone mass and cortical bone porosity best imaged with CT. Synchrotron CT requires a large number of angular projections to reconstruct images with high resolution for detailed and accurate diagnosis. However, this poses great risks and challenges for serial in-vivo human and animal imaging due to a large amount of X-ray radiation dose required that can damage living specimens. Also, longer scan times are associated with increased risk of specimen movement and motion artifact in the reconstructed images. We developed a wavelet-gradient sparsity based algorithm to be utilized as a synchrotron tomography reconstruction technique allowing accurate reconstruction of cortical bone porosity assessed for in-vivo preclinical study which significantly reduces the radiation dose and scan time required while maintaining satisfactory image resolution for diagnosis. The results of our study on a rat forelimb sample imaged in the Biomedical Imaging and Therapy Bending Magnet (BMIT-BM) beamline at the Canadian Light Source show that the proposed algorithm can produce satisfactory image quality with more than 50 percent X-ray dose reduction as indicated by both visual and quantitative-based performance., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Vascular canals in cortical bone during growth and development typically show an anisotropic pattern with canals falling into three main categories: circumferential, radial, and longitudinal. Two major hypotheses attempt to explain the preferred orientations in bone: that vascular canal orientation is optimized to resist a predominant strain direction from functional loading, or that it reflects growth requirements and velocity. We use a controlled growth experiment in broiler chickens to investigate the effect of growth rate on vascular canal orientation. Using feed restriction we set up a fast growing control group and a slow growing restricted group. We compared the microstructure in the humerus and the femur at 42 days of age using synchrotron micro-computed tomography (micro-CT), a three-dimensional (3D) method that visualizes the full canal network. We measured the 3D orientation of each canal in the whole cross-section of the bone cortex using a set of custom ImageJ scripts. Using these orientations we compute laminar, radial, and longitudinal indices that measure the proportion of circumferential, radial, and longitudinal canals, by unit of length, in the cortex. Following previous studies we hypothesized that vascular canal orientation is related to growth, with radial canals linked to a faster growth rate and related to functional loading through a high laminar index in flight bones which reflects torsional loading resulting from active flight. The control group had final body weights that were nearly twice the final weights of the restricted group and higher absolute growth rates. We found consistent patterns in the comparison between the humerus and the femur in both groups, with the humerus having higher laminar and longitudinal indices, and a lower radial index than the femur. The control group had higher radial indices and lower laminar and longitudinal indices in both the humerus and the femur than the restricted group. The higher radial indices in our control group point to a link between radial canals and faster growth, and between laminar canals and slower growth, while the higher laminar indices in the humerus point to a link between circumferential canals and torsional loading. Overall, our results indicate that the orientation of the cortical canal network in a bone is the consequence of a complex interaction between the growth rate of that bone and functional loading environment., (© 2018 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

In the summer of 1845, under the command of Sir John Franklin, 128 officers and men aboard Royal Navy ships HMS Erebus and HMS Terror sailed into Lancaster Sound and entered the waters of Arctic North America. The goal of this expedition was to complete the discovery of a northwest passage by navigating the uncharted area between Barrow Strait and Simpson Strait. Franklin and his crew spent the first winter at Beechey Island, where three crewmen died and were buried. In September 1846, the ships became stranded in ice off the northwest coast of King William Island, where they remained until April 1848. At that time, the crew, reduced to 105, deserted the ships and retreated south along the island's western and southern shores in a desperate attempt to reach the mainland and via the Back River, to obtain aid at a Hudson's Bay Company Post. Sadly, not one individual survived. Previous analyses of bone, hair, and soft tissue samples from expedition remains found that crewmembers' tissues contained elevated lead (Pb) levels, suggesting that Pb poisoning may have contributed to their demise; however, questions remain regarding the timing and degree of exposure and, ultimately, the extent to which the crewmembers may have been impacted. To address this historical question, we investigated three hypotheses. First, if elevated Pb exposure was experienced by the crew during the expedition, we hypothesized that those sailors who survived longer (King William Island vs. Beechey Island) would exhibit more extensive uptake of Pb in their bones and vice versa. Second, we hypothesized that Pb would be elevated in bone microstructural features forming at or near the time of death compared with older tissue. Finally, if Pb exposure played a significant role in the failure of the expedition we hypothesized that bone samples would exhibit evidence of higher and more sustained uptake of Pb than that of a contemporary comparator naval population from the 19th century. To test these hypotheses, we analyzed bone and dental remains of crew members and compared them against samples derived from the Royal Navy cemetery in Antigua. Synchrotron-based high resolution confocal X-ray fluorescence imaging was employed to visualize Pb distribution within bone and tooth microstructures at the micro scale. The data did not support our first hypothesis as Pb distribution within the samples from the two different sites was similar. Evidence of Pb within skeletal microstructural features formed near the time of death lent support to our second hypothesis but consistent evidence of a marked elevation in Pb levels was lacking. Finally, the comparative analysis with the Antigua samples did not support the hypothesis that the Franklin sailors were exposed to an unusually high level of Pb for the time period. Taken all together our skeletal microstructural results do not support the conclusion that Pb played a pivotal role in the loss of Franklin and his crew., Competing Interests: The authors have declared that no competing interests exist.

Cortical bone porosity and specifically the orientation of vascular canals is an area of growing interest in biomedical research and comparative/paleontological anatomy. The potential to explain microstructural adaptation is of great interest. However, the determinants of the development of canal orientation remain unclear. Previous studies of birds have shown higher proportions of circumferential canals (called laminarity) in flight bones than in hindlimb bones, and interpreted this as a sign that circumferential canals are a feature for resistance to the torsional loading created by flight. We defined the laminarity index as the percentage of circumferential canal length out of the total canal length. In this study we examined the vascular canal network in the humerus and femur of a sample of 31 bird and 24 bat species using synchrotron micro-computed tomography (micro-CT) to look for a connection between canal orientation and functional loading. The use of micro-CT provides a full three-dimensional (3D) map of the vascular canal network and provides measurements of the 3D orientation of each canal in the whole cross-section of the bone cortex. We measured several cross-sectional geometric parameters and strength indices including principal and polar area moments of inertia, principal and polar section moduli, circularity, buckling ratio, and a weighted cortical thickness index. We found that bat cortices are relatively thicker and poorly vascularized, whereas those of birds are thinner and more highly vascularized, and that according to our cross-sectional geometric parameters, bird bones have a greater resistance to torsional stress than the bats; in particular, the humerus in birds is more adapted to resist torsional stresses than the femur. Our results show that birds have a significantly (P = 0.031) higher laminarity index than bats, with birds having a mean laminarity index of 0.183 in the humerus and 0.232 in the femur, and bats having a mean laminarity index of 0.118 in the humerus and 0.119 in the femur. Counter to our expectation, the birds had a significantly higher laminarity index in the femur than in the humerus (P = 0.035). To evaluate whether this discrepancy was a consequence of methodology we conducted a comparison between our 3D method and an analogue to two-dimensional (2D) histological measurements. This comparison revealed that 2D methods significantly underestimate (P < 0.001) the amount of longitudinal canals by an average of 20% and significantly overestimate (P < 0.001) the laminarity index by an average of 7.7%, systematically mis-estimating indices of vascular canal orientations. In comparison with our 3D results, our approximated 2D measurement had the same results for comparisons between the birds and bats but found significant differences only in the longitudinal index between the humerus and the femur for both groups. The differences between our 3D and pseudo-2D results indicate that differences between our findings and the literature may be partially based in methodology. Overall, our results do not support the hypothesis that the bones of flight are more laminar, suggesting a complex relation between functional loading and microstructural adaptation., (© 2018 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

The nature of trapped air on submersed ultra-water-repellent interfaces has been investigated. These gaseous layers (plastrons) can last from hours to, in some examples such as the Salvinia molesta fern, months. The interface of submerged superhydrophobic surfaces with carefully controlled micropatterned surface roughness has been probed using synchrotron-based high-resolution X-ray phase tomography. This technique looks in situ, through the aqueous/gas interface in three dimensions. Long-term plastron stability appears to correlate with the appearance of scattered microdroplets <20 μm in diameter that are sandwiched within the 30 μm thick gaseous interfacial layer. These microdroplets are centered on defects or damaged sections within the substrate surface approximately 20-50 μm apart. Such irregularities represent heterogeneous micro/nano-hierarchical structures with varying surface structures and chemistry. The stability of microdroplets is governed by a combination of electrostatic repulsion, contact angle limitations, and a saturated vapor pressure, the latter of which reduces the rate of diffusion of gas out of the air layer, thus increasing underwater longevity. Homogenous surfaces exhibiting purely nano- or micro-regularity do not support such microdroplets, and, as a consequence, plastrons can disappear in <20 h compared with >160 h for surfaces with scattered microdroplets. Such behavior may be a requirement for long-term nonwetting in any system.

Hemicoelus favonii sp. nov. is described and illustrated from Eocene Baltic amber. This new fossil species differs from extant congeners in having 11-segmented antennae; a metathoracic ventrite with large impression in its anterior portion; a pronotum distinctly narrower than the elytral base region; the posterior suture of abdominal ventrite 1 weakly arcuate medially; sharp lateral pronotal margins that are incomplete and distinct in their basal half only; elytral striae that are not grouped in pairs; posterior pronotal angles that are rounded; elytral intestriae 3, 5, 7 and 9 that are distinctly convex; and a comparatively small total body size. The presence of Hemicoelus in Baltic amber suggests that moist, rotting wood was available as a microhabitat in the ancient forest. Beyond the new species description, the systematic placement of Anobium jacquelinae Hawkeswood, Makhan & Turner is discussed. A new fossil record for Microbregma waldwico Bukejs & Alekseev, and the first report of the genus Trichodesma LeConte from Eocene Baltic amber are also presented.

Objectives: Differentiating human from nonhuman fragmented bone is often accomplished using histological methods if the observation of gross morphology proves insufficient. Linearly oriented primary and/or secondary osteonal systems, commonly referred to as osteon bands, are described as a strong indicator of nonhuman bone, particularly the occurrence of multiple bands. This phenomenon has been conventionally documented using two-dimensional (2D) histology, but such analyses are destructive and typically limited to a single cross-section. Progressive developments in high-resolution X-ray imaging, however, allow for the nondestructive three-dimensional (3D) visualization of bone microarchitecture. The primary objective of the current research was to visualize and document the occurrence of osteon banding in adult human cortical bone using high-resolution synchrotron radiation-based micro-Computed Tomography (SR micro-CT)., Materials and Methods: Synchrotron radiation-based micro-CT scanning was carried out at the Canadian Light Source (CLS) national synchrotron facility. The presence or absence of osteon banding was visualized in human skeletal elements from three adult males with representative samples from all regions of the skeleton (n = 129). If present, osteon banding was described and quantified., Results: Results indicated that 23 of 129 human cortical bone specimens exhibited osteon banding, representing 18% of the sample. Linear arrangements of primary and/or secondary osteons were observed in the following skeletal elements: temporal, parietal, frontal, occipital, clavicle, mandible, femur, tibia, ulna, second metatarsal, and sacrum., Discussion: The present work represents the first 3D examination of inter-element variation in osteon banding in adult human cortical bone. Findings indicate that the presence of multiple osteon bands in a single specimen is not diagnostic of nonhuman bone. As such, osteon banding categorically should not be taken as evidence of nonhuman bone in forensic and archaeological contexts., (© 2017 Wiley Periodicals, Inc.)

Introduction: Previously, a finite element (FE) model of the proximal tibia was developed and validated against experimentally measured local subchondral stiffness. This model indicated modest predictions of stiffness (R 2 =0.77, normalized root mean squared error (RMSE%)=16.6%). Trabecular bone though was modeled with isotropic material properties despite its orthotropic anisotropy. The objective of this study was to identify the anisotropic FE modeling approach which best predicted (with largest explained variance and least amount of error) local subchondral bone stiffness at the proximal tibia., Methods: Local stiffness was measured at the subchondral surface of 13 medial/lateral tibial compartments using in situ macro indentation testing. An FE model of each specimen was generated assuming uniform anisotropy with 14 different combinations of cortical- and tibial-specific density-modulus relationships taken from the literature. Two FE models of each specimen were also generated which accounted for the spatial variation of trabecular bone anisotropy directly from clinical CT images using grey-level structure tensor and Cowin's fabric-elasticity equations. Stiffness was calculated using FE and compared to measured stiffness in terms of R 2 and RMSE%., Results: The uniform anisotropic FE model explained 53-74% of the measured stiffness variance, with RMSE% ranging from 12.4 to 245.3%. The models which accounted for spatial variation of trabecular bone anisotropy predicted 76-79% of the variance in stiffness with RMSE% being 11.2-11.5%., Conclusions: Of the 16 evaluated finite element models in this study, the combination of Synder and Schneider (for cortical bone) and Cowin's fabric-elasticity equations (for trabecular bone) best predicted local subchondral bone stiffness., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Molecular human identification has conventionally focused on DNA sampling from dense, weight-bearing cortical bone tissue, typically from femora or tibiae. A comparison of skeletal elements from three contemporary individuals demonstrated that elements with high quantities of cancellous bone yielded nuclear DNA at the highest rates, suggesting that preferentially sampling cortical bone may be suboptimal (Mundorff & Davoren, 2014). Despite these findings, the reason for the differential DNA yields between cortical and cancellous bone tissues remains unknown. The primary goal of this work is to ascertain whether differences in bone microstructure can be used to explain differential nuclear DNA yield among bone tissue types observed by Mundorff and Davoren (2014), with a focus on osteocytes and the three-dimensional (3D) quantification of their associated lacunae. Osteocytes and other bone cells are recognized to house DNA in bone tissue, thus examining the density of their lacunae may explain why nuclear DNA yield rates differ among bone tissue types. Lacunae were visualized and quantified using synchrotron radiation-based micro-Computed Tomographic imaging (SR micro-CT). Volumes of interest (VOIs) from cortical and cancellous bone tissues (n=129) were comparatively analyzed from the three skeletons sampled for Mundorff and Davoren's (2014) study. Analyses tested the primary hypothesis that the abundance and density of osteocytes (inferred from their lacunar spaces) vary between cortical and cancellous bone tissue types. Results demonstrated that osteocyte lacunar abundance and density vary between cortical and cancellous bone tissue types, with cortical bone VOIs containing a higher lacunar abundance and density. We found that the osteocyte lacunar density values are independent of nuclear DNA yield, suggesting an alternative explanation for the higher nuclear DNA yields from bones with greater quantities of cancellous bone tissue. The use of SR micro-CT allowed for a scale of analysis that revealed a high range of variation in lacunar abundance in both tissue types. Moreover, high-resolution SR micro-CT imaging revealed potential soft tissue remnants within marrow spaces not visible macroscopically. It is hypothesized that soft tissue remnants observed among the trabeculae of skeletal elements with high quantities of cancellous bone tissue are responsible for the high nuclear DNA yields. These findings have significant implications for bone-sample selection for nuclear DNA analysis in a forensic context when skeletal remains are recovered from the ground surface., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Synchrotron X-ray Micro Computed Tomography (Micro-CT) is an imaging technique which is increasingly used for non-invasive in vivo preclinical imaging. However, it often requires a large number of projections from many different angles to reconstruct high-quality images leading to significantly high radiation doses and long scan times. To utilize this imaging technique further for in vivo imaging, we need to design reconstruction algorithms that reduce the radiation dose and scan time without reduction of reconstructed image quality. This research is focused on using a combination of gradient-based Douglas-Rachford splitting and discrete wavelet packet shrinkage image denoising methods to design an algorithm for reconstruction of large-scale reduced-view synchrotron Micro-CT images with acceptable quality metrics. These quality metrics are computed by comparing the reconstructed images with a high-dose reference image reconstructed from 1800 equally spaced projections spanning 180°. Visual and quantitative-based performance assessment of a synthetic head phantom and a femoral cortical bone sample imaged in the biomedical imaging and therapy bending magnet beamline at the Canadian Light Source demonstrates that the proposed algorithm is superior to the existing reconstruction algorithms. Using the proposed reconstruction algorithm to reduce the number of projections in synchrotron Micro-CT is an effective way to reduce the overall radiation dose and scan time which improves in vivo imaging protocols.

Purpose: To evaluate the feasibility of using non-radioactive barium as a bone tracer for detection with synchrotron spectral K-edge subtraction (SKES) technique., Methods: Male rats of 1-month old (i.e., developing skeleton) and 8-month old (i.e., skeletally mature) were orally dosed with low dose of barium chloride (33mg/kg/day Ba 2+ ) for 4weeks. The fore and hind limbs were dissected for imaging in projection and computed tomography modes at 100μm and 52μm pixel sizes. The SKES method utilizes a single bent Laue monochromator to prepare a 550eV energy spectrum to encompass the K-edge of barium (37.441keV), for collecting both 'above' and 'below' the K-edge data sets in a single scan., Results: The SKES has a very good focal size, thus limits the 'crossover' and motion artifacts. In juvenile rats, barium was mostly incorporated in the areas of high bone turnover such as at the growth plate and the trabecular surfaces, but also in the cortical bone as the animals were growing at the time of tracer administration. However, the adults incorporated approximately half the concentration and mainly in the areas where bone remodeling was predominant and occasionally in the periosteal and endosteal layers of the diaphyseal cortical bone., Conclusions: The presented methodology is simple to implement and provides both structural and functional information, after labeling with barium, on bone micro-architecture and thus has great potential for in vivo imaging of pre-clinical animal models of musculoskeletal diseases to better understand their mechanisms and to evaluate the efficacy of pharmaceuticals., (Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Accounting for spatial variation of trabecular material anisotropy and orientation can improve the accuracy of quantitative computed tomography-based finite element (FE) modeling of bone. The objective of this study was to investigate the feasibility of quantifying trabecular material anisotropy and orientation using clinical computed tomography (CT). Forty four cubic volumes of interest were obtained from micro-CT images of the human radius. Micro-FE modeling was performed on the samples to obtain orthotropic stiffness entries as well as trabecular orientation. Simulated computed tomography images (0.32, 0.37, and 0.5mm isotropic voxel sizes) were created by resampling micro-CT images with added image noise. The gray-level structure tensor was used to derive fabric eigenvalues and eigenvectors in simulated CT images. For 'best case' comparison purposes, Mean Intercept Length was used to define fabric from micro-CT images. Regression was used in combination with eigenvalues, imaged density and FE to inversely derive the constants used in Cowin and Zysset-Curnier fabric-elasticity equations, and for comparing image derived fabric-elasticity stiffness entries to those obtained using micro-FE. Image derived eigenvectors (which indicated trabecular orientation) were then compared to orientation derived using micro-FE. When using clinically available voxel sizes, gray-level structure tensor derived fabric combined with Cowin's equations was able to explain 94-97% of the variance in orthotropic stiffness entries while Zysset-Curnier equations explained 82-88% of the variance in stiffness. Image derived orientation deviated by 4.4-10.8° from micro-FE derived orientation. Our results indicate potential to account for spatial variation of trabecular material anisotropy and orientation in subject-specific finite element modeling of bone using clinically available CT., (Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.)

Bone is a dynamic tissue which exhibits complex patterns of growth as well as continuous internal turnover (i.e. remodeling). Tracking such changes can be challenging and thus a high resolution imaging-based tracer would provide a powerful new perspective on bone tissue dynamics. This is, particularly so if such a tracer can be detected in 3D. Previously, strontium has been demonstrated to be an effective tracer which can be detected by synchrotron-based dual energy K-edge subtraction (KES) imaging in either 2D or 3D. The use of strontium is, however, limited to very small sample thicknesses due to its low K-edge energy (16.105 keV) and thus is not suitable for in vivo application. Here we establish proof-of-principle for the use of barium as an alternative tracer with a higher K-edge energy (37.441 keV), albeit for ex vivo imaging at the moment, which enables application in larger specimens and has the potential to be developed for in vivo imaging of preclinical animal models. New bone formation within growing rats in 2D and 3D was demonstrated at the Biomedical Imaging and Therapy bending magnet (BMIT-BM) beamline of the Canadian Light Source synchrotron. Comparative x-ray fluorescence imaging confirmed those patterns of uptake detected by KES. This initial work provides a platform for the further development of this tracer and its exploration of applications for in vivo development.

Three-dimensional (3D)-printed poly(ε)-caprolactone (PCL)-based scaffolds are increasingly being explored for cartilage tissue engineering (CTE) applications. However, ensuring that the mechanical properties of these PCL-based constructs are comparable to that of articular cartilage that they are meant to regenerate is an area that has been under-explored. This paper presents the effects of PCL's molecular weight (MW) and scaffold's pore geometric configurations; strand size (SZ), strand spacing (SS), and strand orientation (SO), on mechanical properties of 3D-printed PCL scaffolds. The results illustrate that MW has significant effect on compressive moduli and yield strength of 3D-printed PCL scaffolds. Specifically, PCL with MW of 45 K was a more feasible choice for fabrication of visco-elastic, flexible and load-bearing PCL scaffolds. Furthermore, pore geometric configurations; SZ, SS, and SO, all significantly affect on tensile moduli of scaffolds. However, only SZ and SS have statistically significant effects on compressive moduli and porosity of these scaffolds. That said, inverse linear relationship was observed between porosity and mechanical properties of 3D-printed PCL scaffolds in Pearson's correlation test. Altogether, this study illustrates that modulating MW of PCL and pore geometrical configurations of the scaffolds enabled design and fabrication of PCL scaffolds with mechanical and biomimetic properties that better mimic mechanical behaviour of human articular cartilage. Thus, the modulated PCL scaffold proposed in this study is a framework that offers great potentials for CTE applications.

This study uses synchrotron radiation-based micro-computed tomography (CT) scans to reconstruct three-dimensional networks of Haversian systems in human cortical bone in order to observe and analyse interconnectivity of Haversian systems and the development of total Haversian networks across different ages. A better knowledge of how Haversian systems interact with each other is essential to improve understanding of remodeling mechanisms and bone maintenance; however, previous methodological approaches (e.g. serial sections) did not reveal enough detail to follow the specific morphology of Haversian branching, for example. Accordingly, the aim of the present study was to identify the morphological diversity of branching patterns and transverse connections, and to understand how they change with age. Two types of branching morphologies were identified: lateral branching, resulting in small osteon branches bifurcating off of larger Haversian canals; and dichotomous branching, the formation of two new osteonal branches from one. The reconstructions in this study also suggest that Haversian systems frequently target previously existing systems as a path for their course, resulting in a cross-sectional morphology frequently referred to as 'type II osteons'. Transverse connections were diverse in their course from linear to oblique to curvy. Quantitative assessment of age-related trends indicates that while in younger human individuals transverse connections were most common, in older individuals more evidence of connections resulting from Haversian systems growing inside previously existing systems was found. Despite these changes in morphological characteristics, a relatively constant degree of overall interconnectivity is maintained throughout life. Altogether, the present study reveals important details about Haversian systems and their relation to each other that can be used towards a better understanding of cortical bone remodeling as well as a more accurate interpretation of morphological variants of osteons in cross-sectional microscopy. Permitting visibility of reversal lines, synchrotron radiation-based micro-CT is a valuable tool for the reconstruction of Haversian systems, and future analyses have the potential to further improve understanding of various important aspects of bone growth, maintenance and health., (© 2016 Anatomical Society.)

The study objective was to visualize regions of bone that undergo pathological mineralization and/or remodeling during pathogenesis of osteoarthritis, by employing non-radioactive strontium as a dynamic tracer of bone turnover. Post traumatic osteoarthritis was surgically induced in skeletally mature rats, followed by in vivo micro-CT imaging for 12 weeks to assess bone micro-structural changes. Rats either received strontium ranelate daily for the entire course of study or only last 10 days before euthanization. Distribution of strontium in bone was assessed in two and three dimensions, using electron probe micro-analysis (EPMA) and synchrotron dual energy K-edge subtraction micro-CT (SRμCT), respectively. Considerable early formation of osteophytes around the collateral ligament attachments and margins of articulating surfaces were observed, followed by subchondral sclerosis at the later stages. Accordingly, strontium was heavily incorporated by mineralizing osteophytes at 4, 8, and 12 weeks post-surgery, whereas subchondral bone only incorporated strontium between weeks 8-12.This study showed low dose stable strontium can effectively serve as a dynamic tracer of bone turnover to study pathological bone micro-structural changes, at resolution higher than nuclear medicine. Co-administration of strontium during therapeutic drug intervention may show enormous utility in assessing the efficacy of those compounds upon adaptive bone physiology., (© 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

The primary microstructural unit of cortical bone, the secondary osteon or Haversian system, is widely assumed to have a cylindrical shape. It is generally accepted that osteons are roughly circular in cross-section and deviations from circularity have been attributed to deviations from longitudinal orientation. To our knowledge this idealized geometric relationship, which assumes osteons are perfect cylinders, has not been rigorously explored. As such, we sought to explore two research questions: (i) Does the orientation of osteons in 3D explain variation in shapes visualized in 2D? (ii) Can differences in osteon 3D orientation explain previously reported age-related differences observed in their 2D cross-sectional shape (e.g. more circular shape and decreased area with age)? To address these questions we utilized a combination of 2D histology to identify osteon shape and superimposed micro-computed tomography data to assess osteon orientation in 3D based upon the osteonal canal. Shape was assessed by the inverse of Aspect Ratio (On.AspR(-1), based on a fitted ellipse) - which ranged from 0 (infinitely elongated shape) to 1 (perfectly circular). A sample (n = 27) of human female anterior femoral cortical bone samples from across the human lifespan (20-87 years) were included in the analysis, which involved 1418 osteons. The overall mean measure of On.AspR(-1) was 0.703 (1.42 Aspect Ratio). Mean osteon orientation was 79.1° (90° being longitudinal). While we anticipated a positive relation between orientation and On.AspR(-1), we found the opposite - a weak negative correlation (with more oblique 3D osteon alignment, the 2D shape became more circular as reflected by increased On.AspR(-1)). When analysis of covariance was performed with age and orientation as covariates, the negative relation with orientation was replaced by a significant relation with age alone. This relation with age accounted for 41% of the variation of On.AspR(-1). The results revealed that osteons, on average, are not circular in cross-section and that 3D orientation cannot account for deviation from circular shape. Osteons thus are strictly speaking not cylinders, as they tend to have elliptical cross-sections. We observed that osteons did become less elliptical in cross-section with age independent of orientation - suggesting this is a real change in morphology., (© 2015 Anatomical Society.)

Bone's ability to respond to load-related phenomena and repair microdamage is achieved through the remodeling process, which renews bone by activating groups of cells known as basic multicellular units (BMUs). The products of BMUs, secondary osteons, have been extensively studied via classic two-dimensional techniques, which have provided a wealth of information on how histomorphology relates to skeletal structure and function. Remodeling is critical in maintaining healthy bone tissue; however, in osteoporotic bone, imbalanced resorption results in increased bone fragility and fracture. With increasing life expectancy, such degenerative bone diseases are a growing concern. The three-dimensional (3D) morphology of BMUs and their correlation to function, however, are not well-characterized and little is known about the specific mechanisms that initiate and regulate their activity within cortical bone. We believe a key limitation has been the lack of 3D information about BMU morphology and activity. Thus, this paper reviews methodologies for 3D investigation of cortical bone remodeling and, specifically, structures associated with BMU activity (resorption spaces) and the structures they create (secondary osteons), spanning from histology to modern ex vivo imaging modalities, culminating with the growing potential of in vivo imaging. This collection of papers focuses on the theme of "putting the 'why' back into bone architecture." Remodeling is one of two mechanisms "how" bone structure is dynamically modified and thus an improved 3D understanding of this fundamental process is crucial to ultimately understanding the "why."

Minimally invasive investigation of plant parts (root, stem, leaves, and flower) has good potential to elucidate the dynamics of plant growth, morphology, physiology, and root-rhizosphere interactions. Laboratory based absorption X-ray imaging and computed tomography (CT) systems are extensively used for in situ feasibility studies of plants grown in natural and artificial soil. These techniques have challenges such as low contrast between soil pore space and roots, long X-ray imaging time, and low spatial resolution. In this study, the use of synchrotron (SR) based phase contrast X-ray imaging (PCI) has been demonstrated as a minimally invasive technique for imaging plants. Above ground plant parts and roots of 10 day old canola and wheat seedlings grown in sandy clay loam soil were successfully scanned and reconstructed. Results confirmed that SR-PCI can deliver good quality images to study dynamic and real time processes such as cavitation and water-refilling in plants. The advantages of SR-PCI, effect of X-ray energy, and effective pixel size to study plant samples have been demonstrated. The use of contrast agents to monitor physiological processes in plants was also investigated and discussed.

The most abundant cell in bone, osteocytes form an interconnected system upon which the regulation of healthy bone relies. Although the complete nature of the role of osteocytes has yet to be defined, they are generally accepted to play a part in the sensing of load and the initiation of damage repair. A previous study conducted by our group identified variation of up to 30% in osteocyte lacunar density and morphological parameters between regions of a single cross-section of human femoral shaft; that study, however, was limited to a single individual. The aim of the current study was to determine whether this pattern consistently occurs in healthy young male femora. Anterior, posterior, medial and lateral blocks were prepared from the proximal femoral shaft of seven males and synchrotron radiation micro-CT imaged. Average lacunar densities (± SD) from the anterior, posterior, medial and lateral regions were 23 394 ± 1705, 30 180 ± 4860, 35 946 ± 5990 and 29 678 ± 6081 lacunae per mm(3) of bone tissue, respectively. These values were significantly different between the anterior and both the medial and posterior regions (P < 0.05). The density of the combined anterior and posterior regions was also significantly lower (P = 0.006) than the density of the combined medial and lateral regions. Although no difference was found in predominant orientation, shape differences were found; with the combined anterior-posterior regions having lacunae that were significantly more elongated and less flat than the combined medial-lateral values (P < 0.001). As expected, in this larger study, there was a dramatic difference in lacunar density between the medial and anterior region (up to ~ 54%). The study clearly demonstrates that the high variation seen in osteocyte lacunar density as well as other lacunar parameters, noted in a number of biomechanical, age and pathology studies, are well within the range of normal variation; however, the reasons for and consequences of this variation remain unclear. Lacunar parameters including abundance and shape are being increasingly incorporated into computational modeling of bone biology and this paper represents a more comprehensive description of normal healthy lacunae., (© 2014 Anatomical Society.)